Process for the preparation of 2-nitronaphthalene-4, 8-disulphonic acid



Patented Feb. 27', 1940 UNITED STATE s, PATENT. OFFICE PROCESS FOR THE PREPARATION OF 2- NITRONAPHTHALENE 4,8 DI SULPHONIO ACID Filippo Beretta, Milan, Italy, assignor to Montecatini Societa Generale. per llndustria Mineraria e'Chimica, Milan I Italy Italy, a corporation of I No Drawing. Application'october 31, 1938, Serial No. 238,076. In Italy November 8, 1937 4 Claims. (01. 260-505) The following method has been proposed for the preparation of 2-nitronaphthalene-4,8-disulphonic acid: 1,5-naphthalenedisulphonic acid is dispersed in sulphuric acidat 66 B. and then 5 nitrated in a mixture of sulphuric and nitric acids containing about 5% water. In this way, however, a mixture of the two isomers-2' l-nitro- 4,8-naphthalenedisulphonic acid and 2-nitro-4,8- naphthalenedisulhponic acid is always obtained.

On lowering the temperature of nitration, the

formation'of isomer 2-4,8 prevails, but isomer 1-4.,s is still present, so that it is necessary to. separate the two isomers by means of the different solubility of their sodium salts.

I have now found that when operating at ordi-' discharged into water and treated with magnesia;

the magnesiumsalt formed of the 2-nitronaphthalene-4,8-dis11lphonic acid is washed with water on the filter. Example-360 kg. of 1,5-naphthalenedisu1- phonic acid at 80% and 800 kg. of oleum with a 60% S03 content are introduced into 400 kg. of 35 monohydratedsulphuric acid, taking care that the temperature does not xceed 40 C. The solution is cooled down to C. and 165 kg..of an anhydrous mixture of sulphuric and nitric acids with a 40%HN03 content are slowly added into 40 it while stirring, taking care that the temperature does not exceed C. When the introduction of the nitrating-mixture is finished, the whole mixture is stirred for 6 to 7 hours, at a temperature of 30 to C. The mass is then discharged into water and is treated with kg. of magnesia.

The magnesium salt of the Z-nitronaphthalena- 4,8-disulpl1onic acid is filtered at low temperature and washed with water on the filter. sultingyield is about The 'advantagesobtained by this invention are as follows:

1. A pure, 2-nitronaphthalene-4,8 disulphonic acid, free from isomers, is obtained.

The re-' 2. A reaction with a practically quantitative yield is efiected.

3. The nitration isexecuted at ordinary temperature, avoiding thus the use of brine.

'Having now particularly described and ascertained the nature of my said invention. and in what manner the same is to be performed, 'I declare that what I claim is:

l. Theprocess of manufacture of 2-nitronaphthalene-4,8-disulphonic acid, in which the 1,5- naphthalenedisulphonic acid is subjected to an anhydrous nitration.

2. The process of manufacture of 2 -nitronaphthalenelfi-disulphonic acid, in which the 1,5- naphthalenedisulphonic acid is subjected to an anhydrous nitration at a temperature below 40 C.

3. The process of manufacture of Z-nitronaphtha1ene-4,8-disulphonic acid, in which the 1,5-

naphthalenedisulphonic acid is subjected to an anhydrous nitration at a temperature below 40 0., by dispersing it in monohydrated sulphuric acid and oleum and by making it react with an anhydrous mixture of sulphuric and nitric acids. 4. The process according to claim 3, in which the nitration-mass obtained is treated with magnesia', in order to precipitate the magnesium salt of the 2-nitronaphthalene-4,8 disulphonic acid. FILIPPOBERETTA. 

